1. Field of the Invention
The present invention relates to a process and an apparatus for forming a wood grain simulation pattern on surfaces of synthetic articles and to a novel synthetic wood board made by the process and apparatus.
2. Description of Prior Art
It is known in the art to produce synthetic articles or boards having a wood imitation on one or more surfaces thereof. It is particularly desirable to utilize these products as substitutes for wood in areas where wood can deteriorate quickly due to its environment, such as when used in a ground surface or in contact with water. Another advantage of using synthetic lumber over wood is that there is less maintenance required in keeping a synthetic lumber surface clean and in most instances, the synthetic lumber does not require painting. Another advantage is that synthetic lumber will not warp nor shed sap nor have knots as is the case with lumber and these knots often result in damage to the surface of the lumber which becomes an eyesore. The running of sap is also an eyesore and an inconvenience.
Processes for the production of synthetic lumber and a wood grain imitation is, for example, described in U.S. Pat. Nos. 3,936,518 and 4,141,944. In one of these patents, there is disclosed an extrusion process wherein a formable resin is extruded through a die having an orifice with recesses or grooves around its periphery to form an article having peaks and valleys on its surfaces and while the article is still soft, these peaks are pressed to form portions having high and low densities resulting in a pattern which resembles natural wood. In the other process, the production of the wood layer of the workpiece and then relief embossing texture furrows in portions of the densified covering layer. This type of process is usable for producing articles made only with a synthetic resin having a higher density outer core than the inner core. It is also known to apply an adhesive vinyl on articles, be it plastics or metal, with a pattern printed on the vinyl. It is further known to paint a wood grain imitation on synthetic material or metal, etc.
A further disadvantage of the synthetic lumber above-described having a wood grain imitation thereon is that the surface of the lumber is always relatively smooth. This can be a disadvantage when using the lumber as a flooring as the plastics material is very slippery in its nature and this can cause people to slip and injure themselves.